Perhaps never before in the nation's history have so many key promises to secure Government been made and broken in such quick succession, the Australian Christian Lobby said today.

"Labor is just half way through its second term and it has broken four key promises following its reneging yesterday of its promise to implement poker machine reform by May," ACL's Managing Director Jim Wallace said.

"With the no carbon tax promise and of particular concern to the Christian constituency, the PM had unequivocally committed herself and Labor to defending the Marriage Act, and also confirmed that the Chaplaincy programme would not be secularised, but now the same funds are available for secular counsellors," said Mr Wallace.

"And now a key commitment to secure government, the promise that there would be mandatory pre-commitment legislation to assist poker machine addicts by May, has gone by the board as well."

Mr Wallace said people needed to be able to trust the promises parties made at election time or used to secure government.

"When these sort of promises are routinely broken, it damages our democracy and the compact between politicians and the people.

"Everyone accepts that parties and Prime Ministers sometimes change their minds on policy. However, to keep faith in these circumstances, they have no ethical alternative but to put these changes of election promises to the people at a general election," Mr Wallace said.